The steps in planning for the treatment of blood vessels, such as brain vessels and coronary that have been altered by atherosclerosis, include the angiographic display of those blood vessels and, the quantitative calculation of the diameter, number and length of a stenosis or blockage. Besides morphological statements, such as directly visualizing a stenosis, imaging parameter values of imaging modalities are gaining increasing importance, such as for visualizing parenchymal perfusion distally of the stenosis in the event of a stroke.
Perfusion, which is the circulation of blood through tissue, is one indicator used for diagnosing an region of interest in a patient affected by a stenosis or blockage. By determining perfusion at the capillary level of the region of interest, the effect of the stenosis or blockage of an artery can be assessed and localized directly. The extent of the stenosis or blockage can also be determined. From this information, a therapeutic treatment can be planned, and its success can then be monitored immediately after the intervention by determining the perfusion of the region of interest.
Currently, there are some established perfusion imaging modalities, including positron emission tomography (“PET”), single photon emission computed tomography (“SPECT”), magnetic resonance tomography (“MRT”), or ultrasound reinforced with contrast agent. These imaging modalities offer the ability of quantifying the perfusion status of an region of interest of a patient, such as the parenchyma/myocardium. In general, these imaging modalities can be performed in cases of stable angina pectoris, chronic total blockages, or for risk stratification after a myocardial infarction or when a stroke has occurred.
In principle, the degree of perfusion of the myocardium or the parenchyma supplied by an artery can also be obtained from the data of projection-based and angiographic computed tomography. Analyzing perfusion using projection-based techniques allows for the determination of an intervention's success, and may permit supplementing or changing the therapeutic treatment in the same session.
A general principle for ascertaining the perfusion status of a patient's region of interest, such as the patient's myocardium, using an angiographic X-ray device (cardiac perfusion assessment or “TIMI blush”) is described in U.S. Pat. App. Pub. No. 2007/0041625, which is incorporated by reference herein, and U.S. Pat. App. Pub. No. 2007/0031018, which is incorporated by reference herein.
In general, contrast agent injection is done arterially into an region of interest, and is often done directly into an affected vessel. When the region of interest is captured, the amount of the contrast agent bolus present in the region of interest is often used to determine the perfusion of the region of interest. However, current systems for determining perfusion of a region of interest in a patient use fixed, predefined recording protocols.